eg. Would I find flour? Refined sugar? Were jams and marmalades common then, and if so were they stored in jars as they are now?
The big question is, are you a man living alone? Or do you have a wife, and/or a maid to keep house? If you were anywhere near "affluent," then you'd certainly have a maid or cook or some description to keep house, and perhaps an assistant for her as well.
So, let's just assume that you're upper middle class, so that you're wealthy enough to be even "semi" affluent. That puts you very likely in the top 10% of the population in income, and perhaps even higher. Let's also assume for the sake of simplicity that you live in London, and not some provincial town. You're a wholesale merchant, say, dealing in commodities shipped to Britain from Latin America and West Africa; you don't own the ships, your capital is tied up in your stocks, and the warehouse space you rent on the Isle of Dogs is just within your budget, but as long as you don't have any disasters you can make a decent annual profit by buying goods from shipping companies and distributing them throughout the metropolis.
So, what's in your pantry?
Well, bread, for one thing: white bread in 2lb. or 4lb. loaves, made from roller-milled flour grown all over the world: the United States was the single biggest supplier most years, followed by Russia, India(!), eastern Europe via the Black and Baltic Seas, and by the 1890s, Canada, Australia, and Argentina. And, of course, England, though by 1914 Britain grew less than one fifth of its wheat. Since you're a well-off consumer, your baker is probably a "full-priced" baker, using fine Hungarian flour for much of the bread, and no adulterants like alum. You might also have, from day to day, some variety of "fancy" bread, like rolls, French breads, or pastries. If you were so inclined to consider the latest health trends, you might have Hovis, which was founded in the 1890s, though at the time it was just a milling company which distributed flour to bakers, who then baked the loaves and sold them as Hovis. These would have been made by the same baker, and all of those possibly delivered to your door. You also almost certainly would keep some plain flour, not for baking much, but for general purposes throughout the kitchen (making sauces and soups, for example, which often use wheat flour or corn starch as thickening agents). This would be bought from your baker as well, and was probably a lower-priced English flour, less suited to baking bread but with nicer flavor. You might also have factory-made biscuits. All the major biscuit companies that you know today existed at this point--McVitie's, Carr's, Crawfords, MacFarlane Lang & Co., Huntley & Palmers, Peek Frean, etc. They had massive product lines, with hundreds of different biscuits, and were selling them in penny packets.
What about fruits and vegetables, bought from your local greengrocers? Potatoes at this point were common in British diets, as were starchy roots like carrots, parsnips, swedes, turnips, and so on, as well as onions, garlic, and shallots. These kinds of things kept well and so would probably be available nearly year-round. As far as leafy vegetables, you'd have things like cabbage and kale nearly year-round as well. "Salad" was not really a big thing for Victorians, though, and I've never seen many mentions of lettuce. Your leafy greens would be things that could be boiled, not usually things eaten raw. You would also, at particular times of the year, get tomatoes or beans. I've never seen references to broccoli or cauliflower, but I suspect they were available in Britain by this point, and I've also seen references to artichokes in the 1860s, but that was in France. It's possible to imagine them in Britain, but probably not particularly likely.
As for fruits, there was usually something locally grown in season, so you'd have fresh fruit of some kind for most of the year outside winter; apples, plums, cherries, strawberries, and so on. You wouldn't get much in the way of imported tropical fruits at this point, however. Iberian citrus, perhaps though as I noted a while back in another post, I really don't know when this trade started. It could be eighteenth century or earlier, or perhaps an innovation of the nineteenth century. I've seen references to Spanish oranges from the end of the nineteenth century, but these were oranges that were clearly used for industrial food production, so the actual product arriving in Britain could have been a processed product of some sort (orange oil? essence?) and not fresh. Still, by the 1890s a person of your status might have encountered tropical fruits from time to time. They might not regularly be in your pantry, but my guess is that you've tasted things like bananas and pineapples. Interesting to note as well that Victorians did not like feeding raw fruits to kids. They thought this was too stimulating and unhealthy for young, fragile constitutions, so kids eating fruit would get boiled, stewed versions.
What about processed foods that might be purchased from local shops? By the 1890s, there was a fully developed range of "industrial foods" for sale. These included things like various grades of sugar and treacle, one of the first industrially produced foods, packaged tea and coffee, instant hot chocolate, instant custard, pickles, vinegar, and various sauces like good old "brown sauce" (what flavor is brown sauce, anyway?). Dried oatmeal or porridge would not be unlikely, and patent breakfast foods existed by this point, so it's possible you'd have something like wheatabix or corn flakes. You'd also have, potentially, a pretty big range of tinned products: jams, marmalade, fruits, peas, and beans. There was also a lot of tinned meat, and this is a sticky issue. Certainly the British working classes ate a great deal of canned pork, beef, and mutton from places like the American midwest, Argentina, and Australia and New Zealand. But, if you're semi-affluent, you might not eat that sort of thing, since you'd be able to afford fresh meat.
Moving on to the butcher, you would be more likely to eat chilled meat from distant locales than the tinned stuff. By the 1890s, there were refrigerated steamship connections between Britain and the southern hemisphere, so Argentine and Australasian meats were quite common. If you wanted to splurge a little, then you'd go for good old English meat, but of the three options--tinned, chilled, and fresh--it was definitely the most expensive. I don't know how much meat you'd actually keep in your house at any one time. Leftovers from dinner one night were frequently turned into breakfast or lunch the next day, particularly for the children. "Bubble and Squeak," for example, or "Toad in the Hole," both of which are leftovers processed into new meals. You might actually have an icebox by this point--there was a steady trade between Britain and Scandinavia in ice, and a "cold chain" existed to connect food sources to consumers--but "leftovers" were not something that people were used to keeping around. As for the varieties and cuts of meat you'd have, I think some of them would be familiar to us today--sausages and other smoked or preserved meats like ham and bacon, lamb and pork chops, for example. The more traditional, "big" cuts of meat like legs of lamb were actually going out of style at this point because, as an upper middle class Londoner, you'd have a modern cast-iron stove. Those older cuts of meat really need open hearths to be done properly, and those have become much more rare.
And, lastly, there's dairy products. By 1907, milk was a fully regulated commodity under the surveillance of professional food inspectors appointed by local government agencies; it had long been frequently adulterated or diluted, and thus drew particular attention from the authorities. Butter had undergone a similar process somewhat earlier, but in the case of butter the key issue was distinguishing butter from margarine, and ensuring that one was not mixed with or marketed as the other. But, for you in the 1890s, you'd have milk in your house on a day to day basis, and definitely butter, probably from local sources though it's possible the butter is Danish or Dutch. You'd also have a range of cheeses, and probably fresh eggs as well.
I think that about covers it. Well, actually, I'm positive that I've forgotten loads of stuff, but I think you get the idea. Ask away if you want to know more. My sources for this are basically the major texts in British food history for the past several decades: Derek Oddy's From Plain Fare to Fusion Food, a synthesis of several decades of research by the doyen of British food history; John Burnett's Plenty and Want and J. C. Drummond's The Englishman's Food, two classic accounts; Andrea Broomfield's Food and Cooking in Victorian England; and my own research on bread, forthcoming when I finish the dissertation and find some university to publish it.