Rising commodity prices: should we be concerned? That is a key question facing the food industry. Again this week there was much comment on the issue and the possible impact on the sector. Sainsbury's boss Justin King, for instance, warned suppliers they would have to work hard to justify price increases. Meanwhile, the UK retailer, widely seen to have outperformed its rivals over Christmas, issued its festive numbers this week, alongside the likes of Tesco, M&S and Morrisons.